Sofa



FIG. 1 is a front elevational view of a seat showing my new design in the form of a sofa;

FIG. 2 is a rear view thereof;

FIG. 3 is a right elevational view, the left side being a mirror image thereof; and,

FIG. 4 is a top plan view thereof. 

The ornamental design for a sofa, as shown and described. 